Anaerobic biodegradation of pyrene by Klebsiella sp. LZ6 and its proposed metabolic pathway

ABSTRACT

Pyrene is one of the polycyclic aromatic hydrocarbons, which are a potential threat to ecosystems due to their mutagenicity, carcinogenicity, and teratogenicity. In this study, several bacteria were isolated from oil contaminated sludge and their capacity to biodegrade pyrene was investigated. Of these bacteria, the monoculture strain LZ6 showed the highest pyrene anaerobic biodegradation rate of 33% after 30 days when the initial concentration was 50 mg/L, and was identified as Klebsiella sp. LZ6 by morphological observation, the GENIII technology of Biolog, and 16S rDNA gene sequence analysis. The influence of various culture parameters on the biodegradation of pyrene were evaluated, and Klebsiella sp. LZ6 all showed the high degradation rate at an inoculum of 10–20% (v/v), pH 6.0–8.4, temperature 30–38°C, and initial pyrene concentration of 50–150 mg/L. The intermediate metabolites of the anaerobic biodegradation were analyzed by GC-MS. Several metabolites were identified, such as pyrene, 4,5-dihydro-, phenanthrene, dibenzo-p-dioxin, and 4-hydroxycinnamate acid. The anaerobic metabolic pathway for the degradation of pyrene was inferred by the products. It seems that pyrene was first reduced to pyrene,4,5-dihydro- by the adding of two hydrogen atoms, and then the carbon–carbon bond cleavage at saturated carbon atoms generated phenanthrene.

GRAPHICAL ABSTRACT

KEYWORDS:

• Pyrene
• Klebsiella sp. LZ6
• anaerobic biodegradation
• metabolic pathway
• influence parameters

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [grant number 21777069], [grant number 21808108], the National Key Research and Development Program of China [grant number 2016YFE0112800], the Natural Science Foundation of Jiangsu Province [grant number BK20170997], and the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture.